life—embryology,
biology, etc. Orthodoxy will not in science render false doctrines true, and
Tyndall’s words become a mere mockery and delusion unless they apply to the
embryologist and biologist, as well as to the physicist and chemist.

Twenty
years ago my general principle—an antithetic alternation of generations with a
continuity of germ-cells from generation to generation as the basis of the
cycle of life—was almost within my grasp: that is, had almost been established
by facts of observation. After a few more years of patient research this was
so—at last. Those, and those only, who know and appreciate the history of the
growth of human scientific knowledge—” The Growth of Truth “ (Osler)—can
realize the true import of this. Two of the greatest scientific investigators
of the nine­teenth century were Hermann von Helmholtz and Louis Pasteur. As
investigators they were incomparable, beyond comparison with others or with
each other. What the latter thought about general principles in scientific
research is cited elsewhere in this book, and it may be found in full in his
life, “ La Vie dc Pasteur,” written by Vallery-Radot. The illustrious physicist
and physio­logist, Hermann von Helmholtz, wrote his view in the following beautiful
lines : “ When, from a correct general principle, one develops the conclusions
in special cases of its application, new surprises, for which one was not
previously prepared, always make their appearance. And since the conclusions
unfold, not according to the author’s caprice, but after their own laws, it has
often made the impression upon me that really it was not my own work which I
wrote down, hut merely the work of another. “*